3D30.u3 - Audible Acoustic Levitation
To demonstrate levitation of a foam cone with sound waves in a 1/4-wave tube.
Using a special cut pvc tube piece, prop the driver on its side so the sound port is vertical. Connect the glass tube with plastic sound couplers into the tube of the driver. Make sure there is a cone or disk inside the glass tube before attaching it to the driver. Connect a function generator to the driver and set it to about 220Hz for best results. Adjustments to the frequency and the amplitude can be made to change the position of the object for which we are levitating.
Turn on the function generator to 220 Hz at about 1V. Adjust the amplitude until the object is levitating in an easily viewed position in the tube. Now adjust the frequency or amplitude to show how you can change the position of the pressure anti-node, where the object levitates.
Can operate demo without cork on top of tube, changing from closed ended tube to open ended tube. The amplitude must be increased in order to get the demo to operate comparably.
To observe mulitple nodal positions:
Set the frequency to 2579 Hz. This will produce 5 nodal positions within the tube. Start by setting the function generator on "Stand-by" mode once the frequency and amplitude are set. Open the top and place the object to levitate into the top. Quickly replace the end cap and release the "Stand-by." The object should snap to the nearest node. Slowly decrease the amplitude until the object drops some, then quickly increase the level back up and it will then snap into the next nodal position. **MUST start from the top because at the bottom of the tube is a low pressure area, so there is nothing there to help push the object up the tube.**